Smilax bolavenensis Tagane & Soulad., 2023

Tagane, Shuichiro, Souladeth, Phetlasy & Tamura, Minoru N., 2023, Smilax bolavenensis, a new species of Smilacaceae from southern Laos, Phytotaxa 585 (1), pp. 55-60 : 56-58

Smilax bolavenensis Tagane & Soulad. , sp. nov. ( Figs 1 , 2 )

TYPE: — LAOS. Champasak Province: Paksong District, near Nong Luang Village, Dong Hua Sao National Park ( Bolaven Plateau ), 15°04′44.53″N, 106°12′27.36″E, 1249 m a.s.l., 17 Dec 2019, Souladeth et al . L3342 (holotype: FOF 0006673 ; isotypes BKF, KAG 155707 ) .

Smilax bolavenensis is similar to S. elegantissima Gagnepain (1934b: 619) from Vietnam in having an elongate inflorescence with slightly zigzag rachis longer than 20 cm, but clearly distinguished from it by its terete stem and petiole (vs. 4-angled with each corner narrowly winged) and 42–54-flowered umbels (vs. 7–12).

Climbers to 4 m tall, all parts glabrous. Stems and branches subterete, without prickles and wings. Petioles 3.5–4.5 cm long, subterete; sheaths 1.2–1.7 × 0.7–1 cm. Tendrils up to 10.0 cm long, 1.0– 1.5 cm above from the base of sheath. Lamina ovate-oblong to narrowly ovate, (11.0–)15.2–22.4 × (3.5–) 5.8–13.6 cm, shiny brownish red to brownish yellowish on both surfaces when dry or paler and glaucous abaxially, apex acuminate, acumen up to 0.6 cm long, base cordate, 5-veined, major veins diverging at base of lamina, prominent abaxially, (0.9–) 1.7–2.5 cm interval (at widest point of lamina), connected with reticulate veinlets. Staminate inflorescence composed of spicately disposed umbels, to 33 cm long, 2–4-branched, rachis slightly zigzagged, not winged; umbels sessile, 22 per inflorescence, 42–54- flowered, prophylls ovate-lanceolate, 3.0–4.5 × 1.0– 1.2 mm, apex acuminate; receptacle of an umbel globose, 2.8 mm in diam.; bracteoles 4–5, ovate-triangular to oblong-obovate, 1.6–2.5 × 0.6–1.2 mm, apex acute. Staminate flower (before anthesis), tepals 6, free from base, outer ones ovate-oblong, 2.5–2.9 × 1.3–1.5 mm, inner ones narrowly ovate, 2.0–2.2 × 0.9–1.0 mm long, apex acute, stamens 6, filaments sessile, anthers oblong, 1.3 mm long; pedicels 0.3–0.7 mm long. Pistillate inflorescence, fruits and seeds not seen.

Distribution:— Thus far known only from the Bolaven Plateau.

Habitat:— Montane forests, 1240–1250 m a.s.l., dominated by Fagaceae , Lauraceae and Myrtaceae , along with some subcanopy trees such as Taberaemontana bovina ( Apocynaceae ), Aporosa yunnanensis (Phyllanthaceae) , and Camellia bolavenensis (Theaceae) .

Phenology:— Staminate inflorescence with flower buds collected in December.

Etymology:— Referring to the type locality, Bolaven Plateau.

Vernacular name:— Kheau kheaung Bolaven (; Lao), suggested here. Kheau kheaung in Lao refers to a common name for Smilax .

Preliminary conservation assessment:— Critically endangered (CR). During our five intensive field surveys in Bolaven Plateau 2018–2020, we found only one population with a few individuals in lower montane forest on the top of a plateau where we collected the above two specimens. Therefore, the most appropriate initial assessment of the IUCN conservation status for this species is critically endangered (CR) under criteria D (IUCN 2012). In the Bolaven Plateau, the forests at higher elevation have been decreasing due to dam construction and coffee plantations, which may produce negative effects for S. bolavenensis . Further information on its distribution and number of individuals/ populations is needed to accurately assess its status and conserve this species.

Note: —Among the Smilax species in Laos, S. bolavenensis resembles S. glabra in leaf texture and venation patterns, and both species occur in Bolaven Plateau (specimens of S. glabra: Souladeth et al. L3754, FOF, KAG). However, S. bolavenensis is easily distinguishable from S. glabra by its long-spicately disposed sessile umbels (vs. only 1 umbel axillary in S. glabra ) and its cordate leaf base (vs. cuneate to rounded).

Additional specimen examined:— LAOS. Champasak Province: Paksong District, near Nong Luang Village, Dong Hua Sao National Park (Bolaven Plateau), 15°04′19.26″N, 106°12′38.67″E, 1248 m a.s.l., 10 Dec 2018, Tagane et al. L1964 ( FOF 005293 , FU, KAG 128065 ) .

Figures

FIGURE 1. Smilax bolavenensis (holotype, Souladeth et al. L3342, FOF0006673).

FIGURE 2. Smilax bolavenensis. A. Leafy branch. B. Branch with staminate inflorescence. C. Abaxial leaf surface. D., E. Staminate inflorescence. F. Longitudinal section of a staminate umbel. G. Bracteole. H. Staminate flower bud with bracteoles (left), staminate flower bud (middle), and staminate flower bud outer three tepals and one inner tepal removed showing stamens (right). I. Outer tepals (top) and inner tepals (bottom), adaxial side (left), abaxial side (middle and right). A–C from Tagane et al. L1964 (KAG); D–G from Souladeth et al. L3342 (KAG). Scale bars: F = 5 mm, G–I= 2 mm. Photographed by S. Tagane.